Since we have pagination now on Special: Notifications page, the issue is filed separately from T135307: Special page: Requested notifications are in wrong order .
- On Special:Notifications page with several pages of notifications - click on 'Read' tab and mark some messages from different dates (preferably from from different dates).
- Then, click on 'Unread' - and also mark some notifications as read.
- Go to 'All' tab - the chronological order is broken - sometime on the first page, sometime on the second page.
Very often the chronological order on the first page is preserved - say, for e.g. displaying from notifications from May to February, but the second page may start with notifications dated by April, for example.